Rotary vane pump with pressure biased flow directing end plate

Abstract

In a sliding vane type of rotary pump usable for power steering systems a seal of hour glass shape is provided between the flow directing plate, on the outlet side of the vane rotor and the outlet pressure chamber, to confine exposure of the high pressure of the outlet chamber to the downstream side of the plate within a predetermined area only partially balanced by exposure of the upstream side to such high pressure and to also isolate suction passages from the outlet chamber pressure. The result is a flexing of the flow directing plate at the center toward the pump rotor to reduce rotary clearance and permit the use of thinner and lighter weight flow directing plates.

What is claimed is: 
     
       1. In a rotary vane pump including a housing (1) enclosing a suction chamber (15, 15A) and an outlet chamber (20) from which fluid is discharged under a pump pressure, a cam ring (7) mounted in the housing and having an outer peripheral portion, a rotor (6) mounted within the housing and formed with slots extending radially outward from inner ends relative to a rotor axis, a plurality of vanes (8) slidable within said slots and engageable with the cam ring to form variable volume vane chambers, and flow control surface means (4, 10) fixed to the housing on opposite axial sides of the rotor for conducting fluid from the suction chamber to the vane chambers and from the vane chambers to the outlet chamber, including a flow directing plate (10) having an upstream side confronting the rotor, a downstream side confronting the outlet chamber, circumferentially spaced suction passages (12, 12A) in fluid communication with the suction chamber, and outlet passages (11, 11A) in fluid communication with the outlet chamber, the improvement comprising seal means (21) on the flow directing plate limiting exposure of the downstream side thereof to the pump pressure within a predetermined pressure area (22) thereon having a radially outer chordal portion bordering the peripheral portion of the cam ring in spaced relation to the suction passages, and a radially inner constricted portion spaced radially inwardly of said suction passages and the inner ends of those of the vane slots aligned with the suction passages during rotation of the rotor about the rotor axis for exerting pressure forces on the downstream side of the flow directing plate unbalanced on the upstream side within a radially inner zone through which the rotor axis extends, whereby clearances between the plate and the rotor are reduced by bending of the plate with maximum flexure within said radially inner zone. 
     
     
       2. In a rotary vane pump as set forth in claim 1, said suction passages (12, 12A) extend through said flow directing plate and are closed downstream thereof by said housing. 
     
     
       3. In a rotary vane pump as set forth in claim 1, wherein said flow directing plate includes a peripheral portion supported by said peripheral portion of said cam ring leaving the radially inner zone on the plate unsupported. 
     
     
       4. In a rotary vane pump as set forth in claim 3 including a drive shaft connected to the rotor in axially spaced alignment with the radially inner zone on the upstream side of the flow directing plate.